Frequency measurement system with counting and storage



June 9.67 R. w. STUART, JR.. ETAL 3,328,564

FREQUENCY MEASUREMENT SYSTEM WITH COUNTING AND STORAGE Original FiledFeb. 19. 1960 2 Sheets-Sheet l FIG. 2

PERIODIC CONTROL INVENTORS FIG, ROBERT WILLIAM STUART, JR.

RICHARD H FRANK BY M /Z .-4

ATTORNEYS June 1967 R. w. STUART, JR.. ETAL 3,323,564

FREQUENCY MEASUREMENT SYSTEM WITH COUNTING AND STORAGE Original FiledFeb. 19, 1960 2 Sheets-Sheet 2 TERMINATES PERMITS COUNTING COUNTINGTERMINALA I ,G:

TlME PREDETERMINED .TIME DELAY TERMINAL 7 I v l TERMINAL 5 v W iTERMINAL D U GATE I INVENTORS 7 4 ROBERT WILLIAM STUART, JR.

g RICHARD FRANK BY 721,41 (b -4 ATTORNEYS United States Patent 8 Claims.(Cl. 23592) This application is a continuation of Ser. No. 9,989,

filed Feb. 19, 1960, forCounting and Storage System.

The present invention relates to computing systems, and moreparticularly, to counting, storing and display circuits employed in themeasurement of electrical frequency.

In conventional electronic counting and display systems, anelectrical-impulse counter as, for example, of the decade type, willregister a number of successive counts over a period of time; and then,over a subsequent similar period of time, will store the count fordisplay purposes. A time-sharing use of the counter circuit as anaccumulator and then as a storage device for display is thus involved,the display occurring only at periodic intervals and not continually.Continual displays have been produced, however, with, for example,electronbeam type counters and relay storage matrices and the like, butthe techniques therein-involved are relatively complex and costly.

An object of the present invention, accordingly, is to provide a new andimproved counting and storage system of the character described thatwill permit of continual display or other indication of electricalfrequency.

A further object is to provide a novel system whereby the operator mayoptionally operate the system to produce time-shared counting, storageand display, as above described, or continual counting and continualdisplay at will.

An additional object is to attain the above results with the aid ofelectrical coupling circuits that are not only reliable and fool-proof,but are simple, space-saving and inexpensive, both as to initial costand maintenance.

Other and further objects will be explained hereinafter and will be moreparticularly pointed out in the appended claims.

The invention will now be described in connection with the accompanyingdrawing, FIGURE 1 of which is a block diagram illustrating a countersystem constructed in accordance with the invention;

FIGURE 2 is a partial schematic diagram of a preferred circuit for usein the system of FIGURE 1;

FIGURE 2A is a block diagram of a periodic control for producingsequential control voltages for application to the circuit of FIGURE 2;

FIGURE 3 is a wave-form diagram illustrating the timing of the variousvoltages applied to the circuit of FIGURE 2; and

FIGURE 4 is a partial circuit diagram of a modification.

Referring to FIGURE 1, a conventional eight-digit or eight-place decadecounter is shown, for illustrative purposes, having switching decades,labelled, for example, me. and l mc., meaning ten megacycles and onemegacycle frequency of operation, respectively and 100 kc., 30 kc. and20 kc., meaning one hundred, thirty and twenty kilocycles, respectively.When serially operated, as schematically indicated by the successivehorizontal connections 1 and 1 interconnecting the decades, each decadewill register electrical impulses over a predetermined counting intervaland then pause to store and display that fact during a display interval.Since this operation is so well known, it will not be further discussedherein in order not to detract from the features of novelty of thepresent invention. For the further details of this operation, referencemay be had, for example, to Electronic Measurements 2nd Edition, Termanand Pettit, McGraw Hill, 1952, pages 220 to 222; and Hewlett- PackardJournal, vol. 2, No. 5, January 1951.

As before stated, it is desirable, with this type of counter, topresent, at times, a continual display of the changing count rather thanthe part-time display periodically presented after each switching decadehas counted over a predetermined counting interval. This end isachieved, in accordance with the present invention, by converting theserial operation of the counters to a type of parallel operation inwhich the chain of decades is divided into two parallel groups, such asthe groups I and II of FIGURE 1. The decades of group I are thenoperated exclusively as counting devices, without stopping to store anddisplay; and the decades of the other group II are continually operatedexclusively for storing and display functions, under the control of thecounting decades of the first group. Thus, if switches S and S in FIGURE1 are moved to the upper positions, the serial decade-counting operationconnections 1 and 1 are interrupted.

The decades I, as later explained, upon application of appropriatevoltage pulses, are temporarily stopped in their counting function whilethe corresponding decades II have transferred to them for display thecounts of the respective counters of the decades I. The decade units IIthen function exclusively as storage and display circuits, while thedecade units I alone perform counting functions.

Four of the digits or places, corresponding, in the illustrative exampleof FIGURE 1, to the counts of the 10 mc., 1 mc., kc. and 30 kc. decadesof group I, are thus continually stored and displayed or otherwiseindicated by the corresponding 20 kc. switching decades of group II.This operation might, for example, be used to read the frequency ofelectrical oscillations of an un known frequency. If the operatordesires to follow continually the changes in, say, the last four digitsor places, the switches S and S may be operated and the operatingvoltage pulses may be applied, as later explained, so that theright-hand group Ii of decades will continually display the four digitstransferred from the continually counting decades of group I. Bychanging the counting interval, of course, any desired four digits maybe thus displayed or otherwise indicated.

Preferred circuit details for effecting this result are shown in FIGURE2; illustrated, for purposes of simplicity, as applied to a typicalmultivibrator switching circuit or flip-flop of one decade of group I,and a typical corresponding multivibrator switching circuit of onedecade of group'II. It is, of course, to be understood, that the otherdecade circuits will be similarly interconnected with four connections 3per decade. The left-hand multivibrator circuit of the group I comprisesa pair of conventional electron tube relays of, for example, the triodetype 2, 2, though other types of electron tubes, transistors, and otherrelay or switching devices may, of course, also be employed, as is wellknown. The switching tubes 2, 2' are provided with respective anodes 4,4', cathodes 6, 6 and control electrodes 8, 8'. The anode or outputcircuit of the tube 2 is connected to the control-electrode or inputcircuit of the tube 2' by the resistance-capacitance coupling network10. The controlelectrode 8 of the tube 2 is coupled by a similar network10 to the anode 4' of the tube 2. As is conventional, the anodes 4 and 4are supplied through a common impedance 12 and respective load resistors14 and 14, connected thereto at a common point P, with plate potentialfrom the positive terminal B+ of the plate-supply voltage source B-|-,B. The negative terminal B- may be grounded, as shown, and may connectthrough a common cathode resistor 16, by-passed at 16, to the cathodes 6and 6', of the tubes 2, 2. Grid resistors 18 and 18 are also shownconnected between the respective control electrodes 8 and 8 and the saidB- terminal. The voltage impulses for effecting the counting operationof the tubes 2 and 2' are applied initially from a conventional gatecircuit G, to the terminal I and thence to the common point P.

The right-hand multivibrator circuit is illustrated as of identicalconfiguration, so that it need not be described other than to state thatthe parts thereof have been given the same reference numerals as thecorresponding parts of the circuit 2, 2, though augmented by 100. Thus,for example, the two electron tubes of the right-hand multivibrator arenumbered 102 and 102.

In normal operation, with switch S of FIGURE 1 closed, the multivibratorcircuit 2, 2 and the multivibrator circuit 102, 102', as well as all theother counting circuits, are operating as cascade counting devices inconventional fashion. Thus, an impulse at terminal 1, FIGURE 2, operatesthe circuit 2, 2, and an impulse at terminal II operates the circuit102, 102.

When it is desired to cause the multivibrator circuit 2, 2 to countexclusively and the multivibrator circuit 102,

102 to store exclusively, the operator opens the switch.

S of FIGURE 1, breaking the chain 1, and opens the switch S of FIGURES 1and 2.

A voltage pulse G, shown at the top of FIGURE 3, is applied to the gateG from the terminal A in order to terminate the counting operation of 2,2' and the other counting decadesv of group I for the brief interval ofthe time duration of the pulse. After a predetermined timedelay intervallater, say about'250 micro-seconds, more or less, introduced to allowfor the settling down of the transfer connections 3, etc., a negativere-set pulse V of about 30 micro-seconds, more or less, is applied toterminal 7, and, through the switch S by conductor 1" to the lowerterminal of resistor 118 and theright-hand terminal of rectifier R. Therectifier R normally presents a low-impedance to ground; but when thepulse V is applied, it causes the lower terminal of 118' to drop inpotential below the ground potential B. The control grid electrode 108of the tube 102', is thus affected, re-setting the state of the stage102, 102 which is to function thereafter solely as a storage and displayindicator of the count periodically registered by the counter 2, 2'.Following the trailing or rising edge of the re-set pulse V, a biaspulse V is thereupon supplied to the terminal 5, changing the positivebias +ve normally applied to the right-hand electrode of thelater-described gaseous-discharge tube N. This pulse V may be termed atransfer-command pulse, since, as hereinafter explained, it serves totransfer to the storage-and-dis-play circuit 102, 102 the state of thecounter stage 2, 2. At the termination of the rising right-hand edge ofthe pulse V, (where the pulse V may have a total pulse width of, forexample, about 500 microseconds) a further negative pulse, shown at thebottom of FIGURE 3 is applied to the terminal D, and thence by conductor1 to the lower terminal of resistor 18' and the right-hand terminal ofrectifier R, similar to before-described rectifier R. Since resistor 18connects to the grid 8 of tube 2, the counting stage 2, 2 is therebyreset, so that upon the termination (or rise) of the pulse at terminal A(the uppermost waveform of FIGURE 3), the stage 2, 2 is ready to assumeits counting function, again. Periodically applied pulse sequences, asin FIGURE 3, will result in periodic counting by 2, 2 and storagedisplay of the count by operation of 102, 102.

The ultimate display operated by the stage 102, 102 may assume the formof conventional gas-tube indicators, or other visual devices, labelledDisplay. The term indicate, moreover, as used in the specification andclaimsherein, is intended generically to embrace any kind of display,recording or production of an effect indicative of the state of storageoperation of the circuit.

The timed voltage pulses of FIGURE 3 may be produced in any well-knownmanner, not illustrated in order not to confuse the disclosure withprior-art circuits. The pulse in the uppermost waveform G of FIGURE 3may be produced by a pulse generator such as, for example, a mono-stablemultivibrator of conventional configuration. Referencemay be made, forexample, to Pulse Techniques, Maskowitz and Racker, Prentice Hall, 1951,pages 191206. The delayed pulse V may be produced from the multibratorpulse by any desired further timedelay multivibrator, as explained inthe Pulse Techniques text; or, as another example, by a pulse-delaycircuit of the type described on pages 298 of Principles of Radar, bythe Staff of the Radar School of the Massachusetts Institute ofTechnology, McGraw-Hill, 1946. The pulse V may be produced from thedelay pulse V' by, for example, triggering a further multivibrator, asabove discussed; and the pulse at terminal D may be obtained from stilla further similar time-delay multivibrator, as explained in the abovetexts. Other equally conventional circuits, well known to those skilledin this art, may obviously also be employed. The block diagram of FIGURE2A is intended to embrace all such periodic controls for producing thevoltage pulses of FIGURE 3.

It remains to explain, however, how, once the counting circuit 2, 2 isrendered inoperative by the pulse at terminal A, and the reset pulse Vhas operated upon the stage 102, 102, the transfer-command pulse V setsthe stage 102, 102' at the state of the counter stage 2, 2'.

The coupling circuit 3 comprises an isolating impedance, such as ahigh-value resistor R, a non-linear device N, preferably of thevoltage-threshold-operated type, such as a two-electrodegaseous-discharge tube of the coldelectrode neon type, a source of biaspotential represented by the terminal 5, labelled +ve, and a couplingcapacitance C Other types of non-linear devices may also be employed,though the neon tube is preferred be cause of its reliability, life, lowcost and desirable characteristics, later explained. The resistor R andthe tube N are shown connected in series between the output, namely, theanode 4 of the switching electron tube 2, and the bias-voltage terminal5. The junction 20 between the resistor R and the left-hand electrode ofthe tube N is connected through the coupling capacitance C to the input,namely, to the control electrode 108, of the tube 102.

Assume, for example, that in one of the switching or counting states ofthe multivibrator 2, 2, the tube 2 is cut off and the tube 2 is inconduction. The voltage at the anode 4 may he, say, 140 volts, and thevoltage at the anode 4 may be 60 volts. Since the anode 4 is connectedthrough the isolating resistor R to the left-hand electrode of thedevice N,-the junction 20 will also be maintained, at 140-voltspotential. By adjusting the bias voltage at terminal 5 to approximatelyvolts, the difference in potential across the device N will only be 40voltsa value far below the threshold ionizing voltage necessary topermit the neon gas to ionize or conduct. The coupling circuit 3 isthusineffective. When the bias voltage at terminal 5 is changed, however,say lowered to 20 volts, as by the direct-current voltage impulse V, thethreshold ionizing potential difference is applied and the neon device Nwill conduct, maintaining about a sixtyvolt drop thereacross. Thecoupling circuit 3 thus can couple a sufficiently high negative voltageto the controlelectrode 108 of the multivibrator tube 102 so as to setthe tube 102 to cut off. The tube 102 is now in the same state as thetube 2 and the stage 102, 102 can operate to indicate the count of 2,2'.

The above, however, is a single case, based upon an assumed state. Ingeneral, thervoltage levels in the above example could be of four typesat the time the re-set pulse V is applied at terminal 7:

Plate 4 of Plate 104 of Tube 2 (volts) Tube 102 (volts) Plate 4 of Tube2 Plate 104 of Tube 102 (volts) (volts) The transfer-command pulse V nowdrops the voltage at the right hand electrode of the tube N from, say100 volts down to 20 volts. If tube 2 is non-conducting, its plate 4will be at the illustrative 140 volts; and, by virtue of the connectionof the plate 4 through R to the left-hand electrode of the tube N, asufiicient drop across N occurs to ionize the same and to drop thecontrol electrode 108 to cut-off. The stage 102, 102' thus assumes orhas transferred to it the same state as the counter stage 2, 2.

Similarly, if the tube 2 had been conducting, its plate 4 would havebeen at the 60-volt level, in the above illustration, and the tube Nwould not ionize. The plate 104 of the tube 102 would thus also haveremained at 60 volts (conducting), so that, again the stage 102, 102' isin the same state as the counter stage 2, 2'.

The sloping characteristic of the right-hand edge of the pulse V isuseful to prevent too-much build-up of voltage at 20 before the tube Nhas had time completely to de-ionize.

By connecting output DISPLAY conductors 22 to the anodes 104 and 104,storage information as to the electrical impulse count data transferredthrough the coupling circuit 3 is continually available for operatingany desired indication system. A continual display or other indicationis thus provided of the count periodically achieved by the correspondingcounter stage.

During the time that the stage 2, 2' is counting, and the anode 4 isrising and falling, there is never sufiicient voltage developed across Nto affect the continual storage and display operation of the stage 102,102'. Only at the times of application of the pulse G to terminal A,does the coupling circuit embodying the neon tube N become operative topermit the stage 2, 2 to control the stage 102, 102'. Permanent circuitconnections 3 between the stages 2, 2 and 102, 102' are thus mostconveniently possible at all times, eliminating any necessity forcomplex switching of connections.

An alternative arrangement is shown in FIGURE 4 which eliminates theneceessity of the re-set pulse V. Two similar coupling circuits 3 and 3'are there provided, each having respective isolating-impedance R and Rneon tubes or similar devices N and N, and coupling capacitors C and CIn this case, the coupling circuit 3' between the output (namely, theanode 4' of the tube 2') and the input (namely, the control electrode108' of the tube 102') eliminates the necessity for the re-set voltage Vof FIGURE 2. The sequence of operation for all possible circumstances,may be summarized as follows:

Plate 4 of Plate 104 of Neon Grid that Plate 104 of Tube 2 (volts) Tube102 (volts) condition is cut-01f tube 102 (initially) (Subsequently) 140N fires 108 140 140 60 N fires 108 140 60 140 N fires 108 60 60 60 Nfires 108 60 Note that the first and last columns show that the stage102, 102' is set in the same state as the counter stage 2, 2.

With the systems of FIGURES 2 and 4, moreover, it is preferable toopen-circuit or otherwise disable successive coupling circuits, such asat the conductor 24, to insure against false operation of the system dueto variable ionization delays in the tube N.

It is, of course, to be understood that, from its broadest concepts, theinvention is not restricted, however, to the preferred multivibratortype of switching devices, but is operable with any other type ofswitching device suited for the purpose. Further modifications willoccur to those skilled in the art and all such are considered to fallWithin the spirit and scope of the invention as defined in the appendedclaims.

What is clairned is:

1. A system for measuring the frequency of electrical impulses bycounting the impulses during successive predetermined counting intervalsand for providing a continual display throughout each interval of amultipleplace digital count attained at the end of the precedinginterval, the system comprising in combination, multipleplace digitalimpulse-counting means normally operative to count electrical impulsescontinually, multiple-place digital count storing and displaying meansnormally operative to store and display a multiple-place digital countcontinually While said counting means is counting, count transfer meansadapted, when operative, to transfer a count from said counting means tosaid storing and displaying means, said counting means comprising aplurality of serially connected flip-flop counting circuits, saidstoring and displaying means comprising a corresponding plurality ofstoring and displaying circuits each of which is independent of anddisconnected from the others of said storing and displaying circuits,said transfer means comprising a corresponding plurality of couplingcircuits connecting corresponding flip-flop counting circuits tocorresponding storing and displaying circuits, means for applyingelectrical impulses of unknown frequency to said counting means, andcontrol means independent of said electrical impulses for periodicallyrendering said flip-flop circuits inoperative to count said impulsesonly during transfer intervals of predetermined brief duration betweensaid counting intervals and for rendering all said coupling circuitsoperative to transfer the count to said storing and displaying circuitsonly during said transfer intervals, whereby said impulses are countedcontinually during said counting intervals and the multiple-placedigital count attained at the conclusion of each counting interval iscontinually displayed throughout the succeeding counting interval.

2. The system of claim 1, said control means comprising means forperiodically producing a cut-01f pulse of predetermined brief durationto prevent counting by said counting circuits during said transferintervals, means for producing during said cut-off pulse, first atransfer pulse to render said coupling circuits operative and then areset pulse to condition said counting circuits for the resumption ofcounting at the end of said cut-off pulse.

3. The system of claim 2, said control means further comprising meansfor producing during said cut-01f pulse just prior to said transferpulse a further reset pulse for setting said storing and displayingcircuits in predetermined state.

4. The system of claim 2, further comprising additional couplingcircuits interconnecting said flip-flop counting circuits and saidstoring and displaying circuits, said control means comprising means forperiodically rendering said further coupling circuits operative, duringsaid cutoif pulse and only prior to said transfer pulse, for re-settingsaid storing and displaying circuits in a predetermined state.

5. The system of claim 1, said coupling circuits comprising diodes.

6. The system of claim 1, said coupling circuits comprising gaseousdischarge devices.

7. The system of claim 1, said counting circuits being connected toproduce a decimal counting sequence.

8. The system of claim 1, further comprising selective means forconnecting said storing and displaying circuits as a series countingchain in series with said counting circuits.

References Cited UNITED STATES PATENTS MAYNARD R. WILBUR, PrimaryExaminer.

G. MAIER, Assistant Examiner.

1. A SYSTEM FOR MEASURING THE FREQUENCY OF ELECTRICAL IMPULSES BY COUNTING THE IMPULSES DURING SUCCESSIVE PREDETERMINED COUNTING INTERVALS AND FOR PROVIDING A CONTINUAL DISPLAY THROUGHOUT EACH INTERVAL OF A MULTIPLEPLACE DIGITAL COUNT ATTAINED AT THE END OF THE PRECEDING INTERVAL, THE SYSTEM COMPRISING IN COMBINATION, MULTIPLEPLACE DIGITAL IMPULSE-COUNTING MEANS NORMALLY OPERATIVE TO COUNT ELECTRICAL IMPULSES CONTINUALLY, MULTIPLE-PLACE DIGITAL COUNT STORING AND DISPLAYING MEANS NORMALLY OPERATIVE TO STORE AND DISPLAY A MULTIPLE-PLACE DIGITAL COUNT CONTINUALLY WHILE SAID COUNTING MEANS IS COUNTING, COUNT TRANSFER MEANS ADAPTED, WHEN OPERATIVE, TO TRANSFER A COUNT FROM SAID COUNTING MEANS TO SAID STORING AND DISPLAYING MEANS, SAID COUNTING MEANS COMPRISING A PLURALITY OF SERIALLY CONNECTED FLIP-FLOP COUNTING CIRCUITS, SAID STORING AND DISPLAYING MEANS COMPRISING A CORRESPONDING PLURALITY OF STORING AND DISPLAYING CIRCUITS EACH OF WHICH IS INDEPENDENT OF AND DISCONNECTED FROM THE OTHERS OF SAID STORING AND DISPLAYING CIRCUITS, SAID TRANSFER MEANS COMPRISING A CORRESPONDING PLURALITY OF COUPLING CIRCUITS CONNECTING CORRESPONDING FLIT-FLOP COUNTING CIRCUITS TO CORRESPONDING STORING AND DISPLAYING CIRCUITS, MEANS FOR APPLYING ELECTRICAL IMPULSES OF UNKNOWN FREQUENCY TO SAID COUNTING MEANS, AND CONTROL MEANS INDPENDENT OF SAID ELECTRICAL IMPULSES FOR PERIODICALLY RENDERING SAID FLIP-FLOP CIRCUITS INOPERATIVE TO COUNT SAID IMPULSES ONLY DURING TRANSFER INTERVALS OF PREDETERMINED BRIEF DURATION BETWEEN SAID COUNTING INTERVALS AND FOR RENDERING ALL SAID COUPLING CIRCUITS OPERATIVE TO TRANSFER THE COUNT TO SAID STORING AND DISPLAYING CIRCUITS ONLY DURING SAID TRANSFER INTERVALS, WHEREBY SAID IMPULSES ARE COUNTED CONTINUALLY DURING SAID COUNTING INTERVALS AND THE MULTIPLE-PLACE DIGITAL COUNT ATTAINED AT THE CONCLUSION OF EACH COUNTING INTERVAL IS CONTINUALLY DISPLAYED THROUGHOUT THE SUCCEEDING COUNTING INTERVAL. 